The present invention relates to the collection of solar energy by means of mirrors which direct solar radiation onto solar cells for purposes of generating electrical energy.
Satellites, space probes, space stations or other space vehicles are frequently equipped with so-called solar panels wherein solar radiation is converted into electrical energy by means of solar cells, and the generated electric energy is used to furnish the vehicle with operating power. These solar panels are, for example, constructed in that a frame made of metal or fiber re-inforced plastic holds a substrate constructed as honeycomb plate or as a glass fiber re-inforced foil. The substrate carries the solar cells which may be bonded thereto. The panels are oriented to intercept the solar radiation as close as possible to a right angle for receiving as much radiation power as is possible per unit area. In outer space, the maximum amount is 1.4 kilowatts per square meter.
The cells have a particular mass or weight per unit area of exposure to the sun and they exhibit a particular efficiency. Also, these cells have a cost basis which can be expressed as per unit area of captured radiation (assumed to be the maximum in each instance). One can, therefore, calculate a particular power output per unit weight factor or parameter, and one can also calculate particular cost amount per unit power output under consideration of complete coverage of a radiation receiving area by solar cells. These values or factors are presently about 9.9 kilogram per kilowatt and about $600,000 per kilowatt at a price of a little under $60,000 per square meter for solar cells. It has been proposed to improve these parameters in that the power yield per unit area is increased through concentration of the solar radiation. For example, plane mirrors are arranged on two opposite sides of a large solar panel. These mirrors are inclined by 60.degree. to the solar panel plane and direct thereto additional radiation. The yield was doubled in that fashion as far as captured radiation is concerned. However, the value of mass per unit power and the cost on a per unit power basis could not be correspondingly improved in that manner, because the increased radiation intensity raises the temperature of the solar cells to such an extent that their efficiency drops considerably. In other words, the larger area used for capturing solar radiation did not increase the effective output because the efficiency of producing energy was reduced in the cells on account of raised temperature.